Detection of swine proliferative enteropathy (Lawsonia intracellularis) in slaughtered pigs by histochemical and immunohistochemical techniques

Fragments of terminal ileum were collected from 663 pigs at slaughter from three municipalities of the Rio Grande do Sul state, southern Brazil, to study the efficacy of the macroscopic diagnosis of porcine proliferative enteropathy (PPE). All samples were processed by standard histological methods and stained with a technique that combined Warthin-Starry, alcian blue and hematoxylin-eosin. Sections were simultaneously evaluated for the detection of Lawsonia intracellularis and lesions associated with PPE. Sections in which the occurrence of PPE was suspected were stained by the avidin-biotin immunoperoxidase technique using a polyclonal antiserum to Lawsonia intracellularis, at the dilution of 1:15,000. The histochemical method detected 11 positive sections and immunohistochemical staining detected additional nine positive cases. Twelve out of 643 negative samples had reduced number of goblet cells and adenomatous proliferation without any detectable bacteria. The efficiency of gross evaluation for detecting PPE was measured through the comparison between the results from gross and histological evaluations performed on samples from 219 animals. Although 51 of these samples were considered positive by gross evaluations, only four of them were confirmed as positive by detection of intracellular bacteria associated with characteristic lesions of PPE. The association between gross and histological changes often reported in PPE was not observed in this study.

swine; proliferative enteropathy; histochemical diagnosis; immunohistochemical diagnosis; Lawsonia intracellularis

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